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Preterm birth occurs with 10% of deliveries and yet accounts for more than 85% of perinatal morbidity and mortality. Management of preterm labor prior to delivery includes a multipronged pharmacologic approach targeting utilization of reproductive hormones for continuation of pregnancy, advancement of fetal lung maturity, and the decrease of uterine contractility (tocolysis). This article will review and compare guidelines on pharmacologic management of preterm labor as recommended by the American College of Obstetricians and Gynecologists and the European Association of Perinatal Medicine. The classifications of drugs discussed include exogenous progesterone, corticosteroids, and tocolytics (β-adrenergic agonists, magnesium sulfate, calcium channel blockers, prostaglandin inhibitors, nitrates, and oxytocin receptor blockers). For each of these drug classes, the following information will be presented: mechanism of action, maternal/fetal side effects, and nursing implications.

The aim of this article is to assess the importance of uterine contractility in the implantation of human embryos.Recent findings show that the receptive phase of the endometrium seems to occur in close association with the appearance of pinopodes and endometrial integrins that may be activated by the IL-1 system. Throughout the menstrual cycle wavelike activity patterns of the uterus were identified with adequate wave patterns appearing to be related to successful reproduction in spontaneous cycles and in assisted reproduction. Such patterns are controlled by steroid hormones. Embryo attachment to the predecidualized endometrium and its invasion may be determined by the expression of proteolytic enzymes that require uterine quiescence for implantation. The uterine activity was detected both in vitro and in vivo by using invasive intrauterine pressure and noninvasive ultrasound approaches. Progesterone promotes local vasodilatation and uterine musculature quiescence by inducing nitric oxide synthesis in the decidua. At present, until new evidence emerges to demonstrate otherwise, the effects of progesterone are, directly or indirectly, the only determinant of endometrial preparation for embryo nidation, with the induction of uterine quiescence being one of these effects.Adequate uterine contractility may provide for gamete/embryo transportation through the utero-tubal cavities and successful embryo implantation in spontaneous or assisted reproduction. Inadequate uterine contractility may lead to ectopic pregnancies, miscarriages, retrograde bleeding with dysmenorrhea and endometriosis.

Objective: To compare the safety and efficacy accompanying oral and vaginal misoprostol for cervical ripening. Methods: One thousand four women with medical or obstetric indications for labor induction and unripe cervices were randomly assigned to receive oral or vaginal misoprostol. Initial doses of 200 μg oral and 50 μg vaginal misoprostol were increased to 300 μg oral and 100 μg vaginal after two doses, to a maximum of six doses. Misoprostol was given every 6 hours in both groups. We anticipated that 11% of women treated vaginally would require intervention during the ripening process. Intervention was defined as interruption of the ripening process before labor or Bishop score of 7 or a lack of response to six misoprostol doses. Results: Five hundred three subjects were assigned to oral and 501 to vaginal administration. Oral misoprostol was associated with significantly higher frequencies of intervention (67 [13.3%] versus 42 [8.4%], P = .01), tachysystole (114 [23.6%] versus 85 [17.6%], P = .02), and hyperstimulation (90 [18.6%] versus 66 [13.7%], P = .04). There were no significant differences in cesarean rates (147 [29.2%] versus 120 [24.0%], P = .06), mean number of misoprostol doses used (1.5 versus 1.6, P = .18), or hours from drug administration to delivery (24.5 versus 25.4, P = .77) between the oral and vaginal groups, respectively. The numbers of deliveries between the groups within 24 hours was different (271 [56%] versus 290 [60%], P = .02), oral and vaginal, respectively. No adverse neonatal outcomes were noted. Conclusion: Oral misoprostol has similar efficacy as vaginal misoprostol but is associated with a higher frequency of excessive uterine contractility and intervention.

The clinician is faced with many dilemmas in the diagnosis of preterm labor. The tools at hand (no pun intended) yield subjective information and it is difficult to distinguish true labor from false labor. Because preterm labor is multifactorial in cause and can occur in primiparas, estimating risk for the individual patient is difficult. The cause of the preterm labor in the majority of patients is idiopathic; in this group, the use of salivary estriol as a biochemical marker for preterm labor can increase the accuracy of the diagnosis of true labor. It may also lend confidence to the diagnosis of false labor and may allay anxiety and prevent unnecessary interventions. On the horizon are two noninvasive methods: the EMG, to evaluate uterine contractility, and the collascope, to evaluate the cervix. Both show promise and may provide a more objective assessment of risk for preterm delivery among women with symptoms of preterm labor.

Patients with prolonged decelerations after bupivacaine epidural anesthesia were matched with control patients. It was found that there were no differences in the decrease in mean arterial blood pressure after epidural anesthesia between those with prolonged decelerations (5 +/- 9 mm Hg) and those without (5 +/- 9 mm Hg). Uterine hypertonus was suggested as a cause in the prolonged deceleration group as a result of a higher rate of subjective impressions of uterine hypertonus (82% vs 11%) and more frequent use of terbutaline (30% vs 0%) after epidural anesthesia. With patients with internal uterine pressure monitors used as their own controls, it was also found that basal uterine tone was higher during periods when the deceleration occurred (26 +/- 9 mm Hg) than when it did not (13 +/- 4 mm Hg), and in comparison to windows before epidural anesthesia (12 +/- 5 mm Hg).

A modification of Hendricks' open-end catheter technique for investigating the motility patterns of the nonpregnant uterus has been used to investigate the motility patterns of uteri in women with dysmenorrhea. Patients with dysmenorrhea have an innate hypercontractility of the uterus in the secretory and early menstrual phases demonstrated by an elevated uterine tone, rather than by changes in the intensity or rhythm of the myometrial contractions. Dysmenorrhea is also associated with a “notching” of the descending limb of the contractile wave during early menses. This has been described as the “backing up” effect related to the presence of a bolus of blood at the internal cervical os. The effects of two progestogens and preovulatory methyltestosterone have been investigated by recording the motility patterns of the uterus following therapy, and the results obtained have been discussed.

The influence of balanced anesthesia (BA) on fetal heart rate (FHR) and uterine contraction (UC) patterns was evaluated in pregnant women undergoing emergency cesarean section. The results showed that during operative delivery under BA there was a significant decrease in the beat-to-beat variability of the FHR, most probably due to the anesthetic agent. There was a decrease in uterine contractility expressed by the significant decreases in the peak pressure as well as in the duration of the uterine contractions. Periodic changes in the FHR as decelerations and acclerations disappeared or improved mostly due to the decrease of uterine contractility.

Halogenated anesthetic agents have been used to supplement nitrous oxide during balanced general anesthesia for cesarean delivery to decrease maternal awareness. However, these agents can interfere with uterine contractility and hence have the potential to increase blood loss at the time of cesarean section. To ascertain the effect of the addition of halogenated anesthetic agents for cesarean section anesthesia versus conduction or a simple balanced general anesthetic, we retrospectively assessed three aspects that may reflect operative blood loss at the time of cesarean section. Significantly more women whose balanced general anesthesia for cesarean section was supplemented with a halogenated agent (usually 0.5% halothane) versus those with a conduction or balanced general anesthetic required transfusion therapy, had a postpartum hematocrit less than 30 vol% and had a decrease in the pre- to postdelivery hematocrit of at least 8 vol %. The addition of halogenated anesthetic agents to a balanced nitrous oxide anesthesia for the purpose of decreased maternal awareness must be weighed against the risk incurred from the increased requirement for blood replacement and/or from postpartum anemia.